Measurement of anterior segment changes during accommodation using partial coherence interferometry
True pseudophakic accommodation can only be accomplished by an anterior shift of the optic through ciliary muscle contraction. Partial coherence interferometry (PCI), a recently developed non-invasive optical ranging technique, allows measurement of IOL shifts within the µm range.
In a prospective study, the change in anterior chamber depth (ACD) was measured in 62 pseudophakic eyes of 55 patients (age 54 to 91 years), three months after surgery, using PCI. Six different IOL designs were studied: one-piece plate haptic (Staar AA4203VF), a specially designed acrylic "accommodating" IOL (Morcher Biocomfold Typ43A and Typ43E), 3-piece acrylic (Acrysof MA60BM and Sensar AR40), and 3-piece PMMA with rigid haptics (Dr. Schmidt MC220). Measurements of ACD were performed under cycloplegia (cyclopentolate 1 %) and pharmacologically induced ciliary contraction (pilocarpine 2 %).
The mean amplitude of IOL movement for those IOLs that underwent a forward shift was: one-piece plate haptic 162 µm (mean, repeated measures t-test p<0.05), accommodating Typ43A 117 µm (p<0.01) and Typ43E 222 µm (p<0.05), 3-piece PMMA 56 µm (n.s., p=0.07). The Acrysof and Sensar AR40 shifted backwards: -156 µm (p<0.05) and 37 µm (n.s., p=0.39). Precision of PCI measurement for ACD was 4 µm.
The extent of IOL movement is too small to induce more than 1 D of accommodation in any of our patients. The accommodating IOL does not show more movement than the standard plate haptic IOL. The Acrysof is the only IOL that showed a significant shift posteriorely, however the extent of the shift is small. PCI allows quantification of small IOL movements due to ciliary muscle contraction. This calls for replacement of subjective techniques of assessment such as accommodative amplitudes, which are influenced by factors such as pupil size, by objective quantification of IOL movement in patients with accommodating IOLs.
Department of Ophthalmology, University of Vienna, Austria
AKH-Wien, Währinger Gürtel 18-20, 1090 Wien, Austria